What Top Causes of HVAC Noises & How to Fix It

There are a number of different reasons why your unit could be producing any buzzing, hissing, or humming sounds. An HVAC vibration noise may or may not be a serious issue depending on which sound and what is causing it. Let’s break these down into categories:

There are a number of different reasons why your unit could be producing any buzzing, hissing, or humming sounds. An HVAC vibration noise may or may not be a serious issue depending on which sound and what is causing it. Let’s break these down into categories:

BUZZING:

✅ Loose part vibrating while the unit is turned on

✅ Compressor malfunctioning

✅ Bees or other insects inside air duct system

✅ Unit is freezing up for being overrun

✅ Refrigerant leak

✅ Condenser fan is broken (outside unit is buzzing)

HUMMING:

✅ Compressor is straining

✅ Motor has gone bad

✅ Motor is unbalanced

HISSING:

✅ Leaking Air Duct

✅ Internal valve leak

✅ Compressor pressure is too high

✅ Refrigerant leak in air handler or otherwise

When an HVAC is making loud vibrating noise or buzzing/humming, sometimes it is an issue unrelated to the HVAC function such as bees that have found their way into the air ducts and built a hive during the off season like the fall or winter. This can be a common cause of buzzing in the Sacramento area. It will be an issue of simply removing the hive and assessing if the sound has resolved as a result. However, these noises could also point to a more serious issue that requires an HVAC specialist.

Buzzing could be an electrical problem or even a refrigerant leak. Refrigerants are harmful for the environment. Prevent a noisy HVAC by calling a professional who can properly check where the leak is coming from, repair it and then refill the refrigerant.

If the issue is a refrigerant link, it may expose itself as a hissing sound as well, otherwise, you may hear nothing at all but smell a distinct odor like sulfur or rotten eggs. If you smell gas, immediately leave the premises and notify a gas company as well as the authorities just in case.

When an HVAC is rattling noise it suggests that a part has come loose, stuck or broken within your system. For example, with banging and clanging, you may have a damaged piston or connecting rod.

More often than not, inside the blower a part can become loose or a bearing or other component is failing. If you hear louder banging sounds when the blower is running, shut the system off until you can get help. In any of these cases, an HVAC technician is where to turn for help for HVAC noises.

Turn off your HVAC system and communicate with an HVAC professional. You should stop using the unit until it is repaired or replaced.

The moment that you hear a whistling or squealing coming from your system, the first thing you need to do is shut off your unit immediately. The reason for this is to prevent any of the parts that could be causing the noise from breaking. Here are some reasons that you may be hearing this sound:

✅ Dangerously High Refrigerant Pressure

✅ Airflow is blocked in ducts/supply vents from furniture, dust or debris

✅ Fan Belt in the Blower is breaking

✅ Compressor is failing

After you have turned off the HVAC unit, seek professional help, taking note of what type of sound you are hearing and any thoughts you have about what may be causing it. If the HVAC is making loud noise, this is a warning signal to you. The sound is an indicator or warning signal that something potentially more dangerous could take place if it continues to go unrepaired. Because it might be a refrigerant leak or improper installation issue, it is best to let a professional assess the situation up close.

If your HVAC fan is making noise it may point to your motor needing lubrication, however, it is important that the correct type of lubricant is used (either mineral or synthetic). The oil you use should be detergent free. Common oils used around the house, like WD-40, are too light for this issue. If you are unsure what to use, call an expert for guidance in all HVAC services. You can turn the unit back on once it has been taken care of by a technician’s support or hands.

GRINDING:

✅ Dirt and Debris

✅ Damaged Blower fan bearing or blade

✅ Damaged AC compressor valve

✅ Damaged condenser fan bearings

RATTLING:

✅ Failing Compressor/Compressor clutch

✅ Pulley with failing bearings

If your HVAC makes a rattling noise and there is any dirt or small rock that has made its way into the mechanical components of your AC or furnace this can cause friction. This will begin to break down your unit if it doesn’t get addressed quickly. Any of these concerns call for an HVAC technician to take a look.

A grinding sound coming from your AC usually means there is an issue with a vital part of the system and needs attention before continuing to use it. If you believe that as a result of the damage you may need it fixed, Alpha Mechanical performs AC repair in Sacramento and surrounding areas.

✅ RELAY ISSUE: A repetitive clicking noise in your HVAC means there’s a problem in the relay process in the thermostat that regulates the air temperature

✅ ELECTRICAL PROBLEM: Clicking can indicate an electrical problem connected to the HVAC, which causes the relay to stop working properly.

✅ CONTACTOR: The contactor is the connection between the thermostat and the compressor unit which may be damaged and need replacement which will display as frequent clicking.

✅ IGNITION SYSTEM: If the clicking sound continues after it has already turned on and it is coming from your furnace this could mean your pilot light is out or your electronic ignition is malfunctioning. Normal HVAC sounds include when a furnace first turns on, however, if it persists after turning on that is a different issue.

✅ AC: If the clicking is coming from the AC, it’s either the outside compressor or the inside air handler. Any of the possible causes can be addressed by an HVAC specialist.

If the HVAC is clicking noise, it’s likely a problem that should be fixed by a local professional technician since all of the parts involved in a clicking issue directly affects another part of the system and can break other parts of the unit if not handled with correct care.

In the event that your heating unit is making loud noise such as popping, you may have nothing to worry about. Popping can be a common noise that comes from your ductwork if the heat has not been utilized in a long period of time.

This sound is a result of the cold metal ducts expanding from the rush of sudden warm water after being off and stiff during the off season. This can be true of a location such as Sacramento where it is typical for the units to pop once they are used after a season of no use.

If the popping comes from another source besides the ductwork or if the popping persists after a while of having the unit on, then it might be wise to call a technician to figure out for sure what could be the source. Popping can be caused when the HVAC system’s ductwork expands or contracts due to temperature changes.

Dripping sounds are uncommon but if you do happen to hear anything trickling or dripping it could be a refrigerant leak or issue in your ducts. When your AC cools, it pulls moisture from the air and into the drip pan and if it isn’t draining properly, it can sound like a dripping. Condensation may begin to appear on your AC.

Check the drain tube in the drip pan for blockages preventing the water from flowing out of the unit. If it’s dirty, use compressed air or vinegar to remove the clog and get water flowing again.

A big boom may immediately concern you as a homeowner which makes perfect sense. That is definitely not a sound that you want to be hearing at any point when it comes to your home. A crashing sound or explosion could be a few things including an air duct falling down or carbon particles that have built up and combusted suddenly.

Another thing that can cause this sound is when the furnace is attempting to light (or relight) from a pilot light or electronic ignition unsuccessfully. This will lead to increasing gas build-up within the combustion chamber that will suddenly ignite all at once.

A booming noise doesn’t necessarily mean your HVAC system is blowing up.Nonetheless you should call an HVAC technician to check it out and give you peace of mind. The chamber along with the flue should be inspected and cleaned professionally. If you are a local Sacramento, CA homeowner and hear any loud booms coming from your unit, you may need heating and air conditioning services in Sacramento.